Steelman touted Palin's endorsement as a potential boon in a GOP primary in which all three main candidates have been trying to appeal to conservatives.

Palin's statement praised Steelman as a "commonsense conservative woman" who has stood up to the political establishment "to stop out of control spending and the destructive debt it leaves in its wake."

Steelman, a former treasurer and state senator from Rolla, is running against Congressman Todd Akin and businessman John Brunner in the Aug. 7 primary. The winner will face Democratic U.S. Sen. Claire McCaskill.

A Brunner spokesman expressed surprise by the endorsement, suggesting that Palin "must surely be unaware of Steelman's anti-conservative record."